For cooling and/or aerating bodies of water a number of different types of pumps or spray devices have been devised. These are very often supported at the surface of the body of water by a suitable float arrangement. The prior art devices have employed a vertical tube or housing in which there is an impeller positioned below the surface of the water and rotating about the axis of the tube to force the water out of the top of the tube. In many embodiments the motor was positioned above the top of the tube concentric with the tube axis so that the motor shaft extended vertically down to the impeller. Since the water would exit vertically upward from the top of the tube it would be directed at the motor. This would tend to cause problems such as getting into the motor bearings. This fact plus the desire to spread the water out in a large circular pattern for maximum effect, resulted in the use of various forms of deflectors, etc., so as to cause the water exiting vertically from the top of the tube to turn out horizontally into the desired pattern. Such devices are complicated in the sense that they require additional manufacturing and thus increase the cost. They tend to decrease efficiency by introducing friction, and sometimes static pressure, into the system. These problems are avoided when the present invention is employed, by reason of the fact that the water flow is downward.
The present invention is employed where the requirement is primarily or solely, one of aeration and not cooling. The top of the tube is positioned a short distance below the normal surface level of the water. The impeller is substantially below the top of the tube. Vanes, secured to the tube and positioned about the impeller, are inclined downwardly from the top to the bottom of the tube. The vanes are inclined in the direction opposite to the inclination of the blades on the impeller. The impeller is driven sufficiently fast that a vortex is created from the normal water surface to the top of the impeller. The result is that air is drawn down to the impeller through the center of this vortex. That air is mixed with the water at the impeller and the air and water mixture then is driven down and exits from the pump at a level substantially below the normal water surface.
Embodiments of the type just described have a number of advantages in addition to the increased efficiency obtained by reason of the use of the vanes. These advantages include the following: it takes less energy to force the water downwardly than it does to pump it up in the air and throw it out about the top of the pump, i.e., the apparatus is not moving the water against the pull of gravity. There is not the water loss from evaporation that occurs when the device produces a water spray in the air. In spray type devices it has been the theory that a spray consisting of relatively small droplets is necessary in order to best achieve aeration, but just such a spray also will result in the greatest evaporation. Furthermore, just such a spray is most likely to drift with the wind and, in particular applications, will cause an objectionable mist or water deposit in adjacent areas. In most instances, the surface water is warmer than the temperature of the water at lower levels. Thus, the surface water is least able to hold air. By injecting the air into the cooler areas of the pond, the greater is the likelihood of retention. Furthermore, by injecting the air substantially below the water surface the air must flow up through the higher layers of water before it reaches the surface to be dissipated and during that upward flow it is likely to be picked up and retained by the upper layers of water. Additionally, the prior art devices which deposited the water having the highest air content at the surface of the pond created a disturbance at the surface of the pond, which disturbance was conducive to the loss of air. Such a situation does not, of course, occur in the embodiment described in which the water with the high air content is substantially below the normal water surface when it is released from the pump.
Further objects and advantages will become apparent from the following description.